During hydrocarbon extraction operations, safety equipment is installed for utilisation in the event of catastrophic failure to prevent damage to human life, the environment, assets (tangible and intangible) and also prevent wider societal impacts. This is particularly the case for subsea hydrocarbon extraction where the presence of water can carry contamination from an oil well many thousands of miles, potentially causing huge environmental damage.
During drilling operations and some well intervention operations, the primary barrier utilised to shut a well is the blow out preventer (BOP), which sits on the wellhead. For a subsea well, a riser links the oil rig to the BOP, the riser allowing the passage of drilling equipment, drilling tools, completion equipment and completion tools, particularly conduits such as wellbore tubulars, from the oil rig into the oil well through the BOP. In the event of a major well control event, it is beneficial to be able to sever conduits such as tubulars, including drill pipe and the like, within the riser to, first, permit successful detachment of the rig from the well head and, second, allow the severed conduit to move out of the way from the closure mechanism of the BOP, allowing the blow out preventer to close more easily.
The Deepwater Horizon/Macondo well blowout and explosion incident on 10th April 2010 highlighted a number of technical deficiencies in well control equipment used at the time and which are still in use today. A key issue highlighted was that BOPs, in use, had major limitations in terms of being able to successfully isolate the BOP in a major well control incident when there were ‘non-shearable’ items such as large diameter casing, drill pipe or a drill collar across the BOP. Furthermore, BOPs were designed for severing centralised shearable items across the BOP and not non-centralised shearable items, that may also be under ‘effective compression’.